fix a couple of clang static analyzer warnings.
Most important was a new[] + delete mismatch in ScanFormatDescriptor()
and a couple of possible memory leaks in FileSpec::EnumerateDirectory().


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@181080 91177308-0d34-0410-b5e6-96231b3b80d8